Deflection amplifier



Oct 1963 J. R. CORNELL ETAL 3,109,122

DEFLECTIQN AMPLIFIER Filed April 25, 1960 l0 I2 1 1 SOURCE OF SOURCE OF HORIZONTAL VERTICAL DEFLECTION DEFLECTION SIGNALS SIGNALS (52 53 I FIG.3

(b) I 66 FIG 2 62 HORIZONTAL DEFLECTION SIGNAL 27 &

VERTlCAL I DEFLECTION SIGNAL INVENTORS James R. Cornzll v avid 8. Con 1 top X013) J M04 ATTORNEYS United States Patent 3,109,122 DEFLECTION AMPLIFTER James R. Cornell, Los Angeles, and David B. Congieton,

Torrance, Calif., assignors to The National Cash Register Company, Dayton, Ohio, in corporation of Maryland Filed Apr. 25, 1960, Ser. No. 24,27 7 7 Claims. (Cl. 315-27) The present invention is directed to deflection circuits and more particularly to improvements in circuits for electromagnetic deflection of beams of electrons or other electrical particles over a target area.

'In magnetic deflection arrangements for cathode-ray tubes or other electrical apparatus, it is generally desirable to deflect a beam or beams of electrons over the screen of the cathode-ray tube or the target area to trace a recurrent pattern thereon. The pattern of the trace is often referred to as a scanning pattern or raster. This type of deflection is produced by two continuous and distinct series of deflection signals coupled to respective coordinate deflection windings to produce vertical and horizontal magnetic fields deflecting the beams. The deflection signals that are coupled to the respective deflection windings are generally predetermined repetitive signals whose waveforms are preformed or shaped in order to produce the desired signal waveforms in the deflection windings.

The need for predetermining the shape of the deflection signal waveforms is due to the fact that a deflection winding in a magnetic deflection system forms a low impedance resistive and inductive load, and current variations in deflection signals coupled to the deflection winding produce voltage transients across the winding and in the output of a driving circuit supplying the deflection signals. These voltage transients in the output of the driving circuit produce non-linear current amplification and non-linear drive currents in the deflection Winding which produce undesirable deflection of the beam in [the cathode-ray tube unless compensated for by applying properly shaped deflection signals.

In deflection system for producing rasters on a screen, shaping of the signals to produce desired signal driving currents in the deflection windings is a common expedient, since the required signal Waveform for producing the desired resultant driving signal currents in the deflection windings can be readily predetermined in advance. However, in other general purpose or special equipment, deflection signals, which are not necessarily for the purpose of producing rasters, or are not predetermined repetitive signals, may be subject to occasional or continuous variation in their waveshapes and the transients produced thereby cannot be readily compensated for by prior shaping. Thus, one of the difficulties of the arrangements in the prior art is that no provision has been made for utilizing deflection signals Whose waveforms need not be predetermined, or known in advance, in order to compensate for distortion of the current waveforms in the deflection windings produced by current transients; or, more generally, no provision has been heretofore made to preserve the linear current transfer characteristics of the input deflection signals.

Although the specific problem involved in deflection winding driving circuits provides a direct application of the principles of the invention, the invention overcomes difficulties generally involved in the provision of linear current amplification for reactive, or reactive and resistive loads, wherein direct or alternating currents of both polarities are coupled to a load either continuously or occasionally.

Briefly, the present invention provides for driving reactive loads or resistive and reactive loads wherein it is desired to preserve the linear current waveforms of the input signals; or more simply stated, the present invention provides for minimizing ringing, the condition of transients, by utilizing components in the deflection circuit which provide intrinsic damping. Individual bridge circuits are provided for driving each of the horizontal and vertical coordinate deflection windings controlling the beam of a cathode-ray tube. Each of these deflection windings is connected to form the center leg of a respective bridge circuit. A directly coupled transistor amplifier is provided in each leg of a pair of adjacent outside legs of a respective bridge circuit, and a power supply is provided in each of the remaining outside legs of a respective bridge circuit.

The transistor amplifiers in the adjacent outside legs of each bridge circuit are of the n-p-n and p-n-p type, i.e., transistors of opposite operating polarities. The collectors of these transistor amplifiers in an individual bridge circuit are connected directly to each other and to the same end of the deflection winding, and each emitter of a transistor amplifier is connected in a grounded emitter circuit arrangement with negative feedback wherein each emitter is biased at a substantially fixed or adjustable potential and is connected through the respective power supply forming the adjacent leg of the bridge to the other end of the deflection winding. One of the transistor amplifiers in the bridge circuit is provided for amplifying the input deflection signals while the other transistor amplifier provides an adjustable D.C. positioning current for adjustment of the position of the beam along the respective coordinate axis provided on the screen of the cathode-ray tube. The arrangement of the transistor amplifiers in the bridge circuit is such that each provides independently adjustable sources of opposite polarity amplified currents for the deflection win-ding. Since the currents, so provided on the common collector leads of the pair of transistors in the bridge circuit, are of opposite polarities, the algebraic sum of the collector currents produces a resultant load current signal in the respective deflection winding.

Therefore, it is an object of the present invention to provide an improved magnetic deflection circuit having the foregoing features and advantages.

Another object of the present invention is the provision directly coupled amplifier deflection circuit which provides for linear amplification of deflection signals to thereby produce analog driving currents including D.C. components in a deflection winding of a magnetic deflection system.

Another object of this invention is the provision of a of improved magnetic deflection circuits for a'djustably controlling the position or trace of a beam of electrons or electrical particles on a screen of a cathode-ray tube or other target area.

A further object is to provide linear amplification of analog signals to produce an adjustable net driving current of either polarity in a reactive load.

The manner in which the above and other objects and advantages are attained in accordance with the principles of this invention will be apparent after a detailed consideration of the following drawings, in which:

FIG. 1 is a circuit diagram of the preferred embodiment of the invention;

FIG. 2 illustrates waveforms of typical deflection signals; and

FIG. 3 illustrates the trace of a waveform of a typical deflection signal on the screen of a cathode-ray tube.

Referring now to the drawings there is shown in FIG. 1, individual bridge circuits 18 and 18 for driving respective horizontal-deflection and vertical-deflection windings 14 and 16. Noting bridge circuit 18, the circuit is shown to include a deflection signal amplifier having a transistor 24 connected in series with a power supply source 42 to produce driving currents through horizontaldeflection winding 14 in one direction, and a positioning signal amplifier having a transistor 22 connected in series with another power supply source 40 to produce driving currents through the deflection winding 14 in the opposite direction. As noted in FIG. 1, the bridge circuit 13' is similarly arranged. The deflection signal amplifier included in the horizontal signal bridge circuit 18 is connected to respond to horizontal-deflection signals provided by a source 10, and the deflection signal amplifier included in the vertical signal bridge circuit 18 is connected to respond to vertical-deflection signals provided by a source 12. The transistors 22, 22 in the positioning signal amplifiers of the respective bridge circuits are provided with adjustable bias voltages for controlling their signal output. Since the D.C. positioning current signals and the deflection current signal applied to each of the deflection windings are of opposite polarity, the resultant driving current signal, i.e., the algebraic sum of the currents in each of the deflection windings produces the coordinate magnetic fields for forming the trace of a typical signal waveform 50 on a screen 27 of a cathoderay tube 29, as illustrated in FIG. 3.

Since the bridge driving circuits of the coordinate deflection windings 14 and 16 are identical, only the bridge circuit 18, which is adapted to drive the horizontal-deflection winding 14, connected as a central leg of the bridge, will be further described in detail. Bridge circuit 18 includes a pair of opposite operating polarity p-n-p and n-p-n type transistors 22 and 24, respectively. These transistors are connected together at one end of the deflection winding 14, to form a pair of adjacent outside legs of the bridge circuit; while power supply sources 41 and 4-2 connected together at the other end of deflection winding 14 form the remaining pair of adjacent outside legs of the bridge circuit. Horizontal-deflection signals, derived from source 10, are coupled to the base 23 of the transistor 24. The horizontal-deflection signals are amplified to provide driving current signals in deflection winding 14 for producing a horizontal magnetic field for displaying the signal waveform on the screen 27 of the cathode-ray tube. A typical source of horizontal-deflection signals is a horizontal sweep generator having an output signal voltage or current similar to the typical horizontal-deflection signal current waveform 52, with an adjustable direct current component 53 establishing the D.C. level, as illustrated in FIG. 2a.

Referring momentarily to the vertical-deflection bridge circuit 13, the input circuit coupling arrangement to source 12 for the n-p-n transistor 24 is identical to the input or base circuit of n-p-n transistor 24. The source 12 of vertical-deflection signals may comprise any source of signals varying over a wide frequency range. The amplified vertical-deflection signals provide driving current signals in the deflection winding 16 to produce a vertical magnetic field for displaying the signal waveform on the screen 27 of the cathode-ray tube 29. The typical vertical-deflection input current signal waveform 54, illustrated in FIG. 2b, provides a direct current component during time interval I to Z and includes an adjustable direct current component 55 which establishes the D.C. level.

Referring back to the horizontal-deflection bridge circuit 18, the input or base circuit of the transistor 22 is adjustable to control the amplitude of the D.C. positioning signal current 60 (FIG. 20) coupled to the horizontal-deflection winding 14. This base circuit includes an adjustable voltage divider having the form of a resistor element 33, connected across a power supply source 40, and a movable tap 35. The base 25 is connected to the movable tap 35 to provide an adjustable base signal current for controlling the current amplitude of the collector current, i.e., the D.C. positioning signal current. Collectors 26 and 28 of respective transistors 22 and 24 are connected directly together by a common lead 30,

4 which lead is also connected directly to one end of the horizontal-deflection Winding 14 forming the central leg of the bridge circuit, as indicated in FIG. 1. Emitters 32, 34- of the respective transistors 22 and 24 are connected to the other end of the horizontal-deflection winding 14 through emitter resistors 36, 38 respectively, and power supply sources 40, 42, respectively. The power supply sources 40 and 42 form the remaining pair of adjacent outside legs of the bridge circuit supplying the drive current to the horizontal-deflection winding 14.

Transistors 22 and 24 provide high dynamic or impedances in their respective collector output circuits producing intrinsic damping whereby the current amplification in the respective amplifier circuits is substantially linear over the range of operation. As a result, drive currents in the horizontal-deflection windings 14 are substantially independent of voltage transients produced in the deflection Winding 14. As a result of this intrinsic damping in both bridge circuits, the input signal waveforms of the vertical-deflection signal, e.g., the verticaldeflection signal waveform 54 illustrated in FIG. 2b, can be accurately positioned and reproduced on the screen 27 of the cathode-ray tube 29, as illustrated in FIG. 3.

In operation, typical coordinate horizontal-deflection and vertical-deflection current Waveforms 52 and 54, illustrated in FIGS. 2a and 2b, respectively, are coupled from sources 19 and 12 to the input or base circuits of transistors 24 and 24, respectively. The current 52 is amplified to produce a current waveform 62 whose level is adjusted by the level of D.C. component 63, as shown in FIG. 20. This current waveform 62 in winding 14 is opposite in polarity from the D.C. positioning current waveform 60, which is also shown in FIG. 2c. In the horizontal-deflection winding 14, the resultant signal driving current waveform 61, representing the algebraic sum of these currents, increases in amplitude linearly, as shown.

The typical horizontal-deflection or sweep current waveform 61, which is disposed symmetrically about the signal reference axis I of the graph, as shown in FIG. 2c, is coupled to the horizontal-deflection winding 14, the common load impedance for both transistors 22 and 24. Coordinate magnetic fields produced by permanent magnets or positioning signal currents in the deflection windings are provided to deflect the beam for initial positioning of the beam on the screen 27. Horizontal-deflection winding driving currents, e.g., the typical horizontal or sweep-deflection current waveform 61 shown in FIG. 20, will, in absence of any vertical-deflection signal, produce horizontal magnetic fields varying uniformly in amplitude from a predetermined amplitude in one direction to a predetermined amplitude in the opposite direction to deflect the beam uniformly across the screen 27 in a horizontal direction Within the time period of the signal. As previously indicated, the D.C. positioning current waveform 60 can be readily adjusted to provide the symmetrically disposed resultant-signal drive current waveform 61 for driving the horizontal-deflection Winding 14, whereby the trace of the horizontally deflected beam of electrons is centered horizontally on the screen 27. It should be clear now that adjustment of the amplitude of either the D.C. positioning-currents 60 or the D.C. level 63 of the deflection signal current waveform 62 (FIG. 2c) can be employed to position the midpoint of the trace of a horizontally deflected beam either to the left or to the right of a vertical coordinate axis 64, shown in FIG. 3, which axis passes through the center of the screen 27.

The vertical-deflection bridge circuit 18 is similarly arranged and operated to provide an amplified current waveform 57 whose level is adjusted by the level of D.C. component 58, as shown in FIG. 2d. This current waveform 57 in winding 16 is opposite in polarity from the D.C. positioning current waveform 56, which is also shown in FIG. 2d. In the vertical-deflection winding 16,

the resultant signal driving current waveform 51 represents the algebraic sum of these currents.

The resultant overall direction of deflection of a beam of electrons in a cathode-ray tube 29 will depend upon the direction of the resultant magnetic fields produced by the drive currents in the coordinate deflection windings l4 and 16. The direction of the magnetic fields depends upon the direction of the drive currents in the windings, and the direction in which the windings are wound. For the purpose of illustration, it will be assumed that a portion of a resultant drive current in the horizontal-deflection winding, e.g., current waveform 61, which is below the signal reference axis I (FIG. 20), will deflect a beam of electrons to the left side of the screens vertical axis 64, as viewed in FIG. 3, and a portion of the current waveform 61 above the signal reference axis I will deflect a beam to the right of the screens vertical axis 64. The screens vertical axis 64 is specified because in normal operation a beam of electrons will be deflected from the horizontal axis 66, passing through the center of the screen, by vertical magnetic fields produced by the vertical-deflection Winding driving currents, e.g., resultant signal current 51. Also for the purpose of illustration, it will be assumed that the direction in which the coils of the vertical-deflection winding 16 are wound, is such that a portion of the resultant vertical-deflection signal current waveform, e.g., signal current waveform 51 (FIG. 2d), which is below the signal reference axis will deflect the beam of electrons below the horizontal axis 66 on the screen 27 and a portion of the resultant signal current waveform 51, above the signal reference axis, will deflect the beam above the horizontal axis 66.

Having noted the functional operation of producing a desired deflection of the beam of electrons resulting from the flow of a drive signal current 61 through the horizontal-deflection winding 14, and the flow of a drive signal current 51 through the vertical-deflection winding 16, certain of the circuit operations and characteristics will next be described in greater detail. A horizontaldeflection or sweep signal current 52 (FIG. 2a) coupled to the input or base circuit of the transistor 24, including the emitter resistor 33 and a variable current supply 21, will produce amplified horizontal-deflection signal currents, having a waveform 62, in the output or collector circuit. The linear current amplification characteristics of the transistor 24 will tolerate large voltage transients of the horizontal-deflection winding 14, due to current variations in the winding 14, without significant changes in linearity of the driving current in the winding 14 and the collector circuits.

Collector current flow through the emitter resistor 38 introduces a negative feedback in the input or base circuit to improve the stability and linear characteristics of the amplifier circuit. The direction of current flow through the n-p-n type transistor 24 is from the collector 28 to the emitter 34, as indicated by the potential of the power supply source 42 which is connected in the colector circuit. The variable current supply 21 is provided for adjusting the DC. level of current 53 to control the DC. level of the input deflection signal currents, e.g., signal current 52, illustrated in FIGS. 2a and 212.

It should be clear that since the transistors 22 and 24, of p-n-p and n-p-n type, respectively, function to produce driving currents of opposite polarities in the center leg of the bridge circuit; the use of transistors 22 and 24 in the circuit can be interchanged without affecting the functional requirement that the collector currents are of opposite polarities in the bridge circuit, by reversing the polarity of the respective input signals and the power supplies to provide the proper polarities for the types of transistors provided in the respective amplifier circuits.

The input circuit for the transistor 22 provides a DC. signal current input to the base, or emitter to base DC.

bias voltage, which is adjustable by varying the position of the movable tap 35 on the resistor element 33. The amplitude or DC level of the DC. positioning signal current in the collector circuit, including the horizontaldeflection winding 14, is controlled by the adjustment of either the DC. bias voltage coupled to the base 25 or the DC. bias voltage coupled to the base 23.

The flow of collector current through the emitter resistor 36 provides a degenerative or negative feedback in the input or base circuit in response to signal current variations in the collector circuit to improve the stability and the linear characteristics of the positioning signal current amplifier circuit 18. Transient voltages are produced in the collector circuit in response to current amplitude variations of driving currents in the respective deflection winding. As noted previously, the dynamic impedance of the transistors is high and the response of the amplifier circuits to transients is thus minimized; however, the stability of the amplifier circuits is further improved by the provision of negative or degenerative feedback in the emitter circuits of the transistors.

It should be noted that in the absence of directly coupled amplifiers of the type described in the present invention for the vertical-deflection winding 16, a typical vertical-deflection signal 54, shown in FIG. 211, having a steady D.C. component, would be distorted due to decay or droop in the level of the amplified vertical-deflection signal current 57 and the resultant signal current 51 (FIG. 2d) during the interval from time to time t The directly coupled amplifier circuits for both the vertical and horizontal-deflection windings l4 and 16 provide for coupling of DC. deflection driving signal components of signals 54 and 52, to prevent distortion of the signals. Further, the D0. levels 53 and 55 of the input deflection signals, as amplified and coupled to the corresponding horizontal and vertical-deflection windings 14 and 15 in the respective collector circuits, also control the DC. levels of the driving currents in the respective deflection windings and the DC. levels of the coordinate magnetic fields controlling the position of the trace of the signal waveform St on the screen 27, as illustrated in FIG. 3.

While the form of the invention shown and described herein is admirably adapted to fulfill the objects primarily stated, it is to be understood that it is not intended to confine the invention to the one form or embodiment disclosed herein, for it is susceptible of embodiment in various other forms, for example, the invention is applicable to driving loads generally but is particularly advantageous for driving loads having a reactance or both a reactance and a resistance where it is desired to preserve the current transfer characteristics or simply to minimize ringing, the condition of transients, by intrinsic damp- What is claimed is:

1. In a deflection system including a deflection yoke having coordinate deflection windings for producing individually varying coordinate magnetic fields, a deflection winding driving circuit for producing deflection signal driving currents in a respective deflection winding comprising: first amplifier circuit means, including a transistor of a first operating polarity having an input, and a high dynamic output impedance connected across a deflection winding for amplifying and coupling deflection signals in one direction across the respective deflection winding; and second amplifier circuit means including a transistor of a second operating polarity having an input and a high dynamic output impedance connected across the deflection winding which is connected to said first amplifier, to couple a DC. positioning signal of a second, opposite direction across said winding to produce a single resultant drive current signal in said winding.

2. In a deflection system including a deflection yoke having individual vertical and horizontal-deflection windings for producing individually varying horizontal and vertical magnetic fields, a driving circuit for each winding for producing deflection signal driving currents in the respective winding comprising: directly coupled amplifier circuit means including a transistor of a first operating polarity, having an input and a high dynamic output irnpedance, connected across a deflection winding for producing and coupling linearly amplified analog deflection signal currents to said winding in response to analog deflection signals coupled to said input; and directly coupled positioning signal circuit means including a transistor of a second operating polarity having an input and a high dynamic output impedance, connected across said deflection winding which is coupled to said amplifier, for producing and coupling adjustable D.C. positioning signal currents to said winding wherein the DC. positioning signal currents and analog currents coupled to the winding are in opposition.

3. In a magnetic deflection system including a deflection yoke having a pair of coordinate deflection windings for producing individually varying coordinate magnetic fields, individual driving circuits for said windings for producin deflection driving currents in said windings, each of said driving circuits comprising: circuit means including a pair of transistors or" opposite operating polarities, each of said transistors including an emitter, a base and a collector and having an input and an output and linear current amplification characteristics for producing linear arnplification of deflection driving current signals in a respective deflection winding; said circuit means further including input circuit means for directly coupling deflection signals to the input of a first transistor for producing amplified deflection signal currents in its output and coupling a direct current to the input of a second transistor for producing D.C. positioning signal currents in its output; said circuit means further including output circuit means connecting the collectors of the transistors directly to each other and to one end of the respective deflection winding and power supply means coupling the emitters to the other end of the respective deflection winding for directly coupling amplified signal currents in opposition to the respective deflection winding including amplified current deflection signal currents in the output of the first transistor and DC. positioning signal currents in the output of the second transistor, whereby resultant driving current signals are produced in the respective deflection winding for generating a magnetic field varying in amplitude according to the deflection signals coupled to the input of the first transistor.

4. In a magnetic deflection system including a deflection yoke having first and second coordinate deflection windings for producing individually varying coordinate magnetic fields, individual driving circuits for said deflection windings for producing driving currents in said windings; each of said driving circuits comprising: circuit means including a pair of transistors of p-n-p and n-p-n types wherein each of said transistors has an emitter, a base and a collector; said circuit means further including input circuit means individual to each transistor for directly coupling deflection signals to the base of a first transistor of the pair for producing amplified deflection signal currents in its collector circuit, and coupling an adjustable DC. voltage between the emitter and the base of a second transistor of the pair for producing adjustable D.C. positioning signal currents in its collector circuit; said circuit means further including collector circuit means connecting the collectors of the transistors directly to each other and to one end of a first deflection winding and including coupling the emitters to the other end of the first deflection winding through individual power supplies for said transistors for directly coupling current signals to the first deflection winding in opposition including the amplified deflection signal currents in the collector circuit of the first transistor and the DC. positioning signal currents in the collector circuit of the second transistor whereby resultant driving current signals are produced in the respective first and second deflection 8 windings by respective driving circuits for generating respective magnetic fields which vary in amplitude linearly with the respective deflection signals coupled to the respective bases of the first transistors and which fields vary in level with the level of respective adjustable direct current coupled to the second transistors.

5. In a magnetic deflection system for cathode-ray tubes including a screen and a deflection yoke having a horizontal-deflection winding and a vertical-deflection winding, the combination comprising: a first bridge circuit for producing driving current signals in said horizontal-deflection winding comprising circuit means for individually amplifying horizontal-deflection signals and horizontal positioning signal currents to produce amplified deflection signals and horizontal positioning signal cur rents, respectively, and coupling said amplified deflection and positioning signals across said horizontal-deflection winding in opposition; said amplifier circuit means including a pair of transistors of opposite polarities, each having a collector, a base and an emitter, wherein each of said transistors are connected in a respective leg of said first bridge circuit and the collectors are connected to the same end of said horizontal-deflection winding which winding is connected in the center leg of said bridge circuit to produce resultant driving signal currents in said horizontal-deflection windings; a second bridge circuit for producing driving signal currents in said vertical-deflection winding comprising circuit means for individually amplitying vertical-deflection signals and vertical positioning current signals to produce amplified deflection signals and vertical positioning signals and coupling said amplified signals across said vertical-deflection winding in opposition; said vertical-deflection signal amplifier circuit means including a pair of transistors of opposite polarities, each having a collector, a base and an emitter, wherein each of said latter pair of transistors are connected in a respective leg of said second bridge circuit and the collectors are connected to a common end of said verticaldeflection winding which winding is connected in the center leg of said second bridge circuit to produce resultant driving signal currents in said vertical-deflection winding; said horizontal and vertical-deflection windings being responsive to respective resultant driving signal currents to produce respective horizontal and vertical magnetic fields for deflecting a beam of electrons in said cathoderay tube to trace a linear waveform of the vertical dcfiection signals on the screen of said tube.

6. In a magnetic-deflection system for cathode-ray tubes including a screen and a deflection yoke having a horizontal-deflection winding and a vertical-deflection winding for deflecting a beam of electrons in the cathoderay tube, the combination comprising: a horizontal-deflection bridge circuit for producing horizontal-deflection signal driving currents in said horizontal-deflection winding including horizontal-deflection signal current amplifier circuit means and horizontal-positioning signal current amplifier circuit means having respective output circuits individually connected across said horizontal-deflection winding; said amplifier circuit means including first and second transistors of p-n-p and n-p-n types, each having a collector, a base and an emitter, wherein each of said transistors is connected in a respective leg of a pair of adjacent outside legs of said horizontal bridge circuit and the collectors are connected to the same end of said horizontal winding, and input circuit means for coupling horizontal-sweep deflection signals to the base of a first transistor and an adjustable DC. current to the base of the second transistor to produce amplified horizontalsweep deflection signal currents of one polarity and horizontal positioning signal currents of the other polarity in respective collector circuits and resultant driving current signals in said horizontal Winding which are the algebraic sum of said amplified deflection and horizontal positioning signal currents; a vertical-deflection bridge circuit for producing vertical -deflection signal driving currents in said Oct. 29, 1963 Filed July 22, 1957 APPARATUS FOR RECORDING RECEIVED ECHOES W. GRADA ETAL 3 Sheets-Sheet 1 IN YE N T0 R5 Walter GPA DA Friedrich Wilhelm KA LLME YE R 525mm [1/ ou RTToRA/E 

1. IN A DEFLECTION SYSTEM INCLUDING A DEFLECTION YOKE HAVING COORDINATE DEFLECTION WINDINGS FOR PRODUCING INDIVIDUALLY VARYING COORDINATE MAGNETIC FIELDS, A DEFLECTION WINDING DRIVING CIRCUIT FOR PRODUCING DEFLECTION SIGNAL DRIVING CURRENTS IN A RESPECTIVE DEFLECTION WINDING COMPRISING: FIRST AMPLIFIER CIRCUIT MEANS, INCLUDING A TRANSISTOR OF A FIRST OPERATING POLARITY HAVING AN INPUT, AND A HIGH DYNAMIC OUTPUT IMPEDANCE CONNECTED ACROSS A DEFLECTION WINDING FOR AMPLIFYING AND COUPLING DEFLECTION SIGNALS IN ONE DIRECTION ACROSS THE RESPECTIVE DEFLECTION WINDING; AND SECOND AMPLIFIER CIRCUIT MEANS INCLUDING A TRANSISTOR OF A SECOND OPERATING POLARITY HAVING AN INPUT AND A HIGH DYNAMIC OUTPUT IMPEDANCE CONNECTED ACROSS THE DEFLECTION WINDING WHICH IS CONNECTED TO SAID FIRST AMPLIFIER, TO COUPLE A D.C. POSITIONING SIGNAL OF A SECOND, OPPOSITE DIRECTION ACROSS SAID WINDING TO PRODUCE A SINGLE RESULTANT DRIVE CURRENT SIGNAL IN SAID WINDING. 